Pteridofyyteissä

Pteridophytes are a diverse group of vascular plants that reproduce via spores. This division includes ferns, horsetails, and clubmosses. Unlike seed-bearing plants, pteridophytes lack flowers and seeds, relying instead on the dispersal of lightweight spores to propagate. Their life cycle is characterized by alternation of generations, involving a prominent sporophyte (the familiar leafy plant) and a much smaller, short-lived gametophyte.

The sporophyte generation is diploid and produces spores through meiosis. These spores germinate to form the haploid gametophyte, which is typically a small, heart-shaped structure called a prothallus. The gametophyte produces gametes (sperm and eggs), and fertilization requires the presence of water for the sperm to swim to the egg. The resulting zygote develops into a new sporophyte, completing the cycle.

Pteridophytes are found in a wide range of habitats, though many prefer moist, shaded environments due to their reliance on water for reproduction. They play important ecological roles, contributing to soil formation, habitat diversity, and as food sources for various animals. Fossil evidence suggests that pteridophytes were dominant plants in ancient ecosystems, forming vast forests during the Carboniferous period. Their evolutionary significance lies in their development of vascular tissues (xylem and phloem) for efficient water and nutrient transport, a crucial adaptation that allowed plants to colonize terrestrial environments.